1. Field of the Invention
The present invention relates to a system and method for accessing a node of a network, and more particularly to a system and method for accessing a node of a private network via the Internet. The present application is based on Korean Patent Application No. 2000-50259, which is incorporated herein by reference.
2. Description of the Background Art
Thanks to a technology advancement, information and communication devices such as computers, faxes, modems and telephones of an office can now be efficiently used in connection with each other within one network.
Most of the Small Office Home Office (SOHO) or home networks are private networks which are not assigned with global IP addresses.
A network without the global IP address should be connected to an Internet Service Provider (ISP) and assigned with a temporary global IP address, to access an external network.
Meanwhile, even if the SOHO or home network has the global IP address, only an access node of the office has the global IP address. Accordingly, other information and communication devices in the SOHO or home network are assigned with private IP addresses for use therewithin.
The private IP address is either assigned by a network administrator, or dynamically assigned by a Dynamic Host Configuration Protocol (DHCP).
In order to access a node of an external network, value of the nodes has to be converted from the private IP address into a global IP address.
When an internal node having a private IP address uses an external server via the Internet, a gateway in the access node of the private network assigns external port value to the internal node and sends out a packet by using a Network Address Port Translation (NAPT).
When receiving a response packet from the external network, the gateway restores the original private IP address and port value based on a port value included in the packet.
Here, the port value may be varied according to a type of communication protocols being used such as http, FTP and TELNET.
In the private network having the private IP address and constructed based on the NAPT, however, it is impossible for the other networks to obtain the port values of the nodes and send a packet to the nodes of the private network.